1. Field of the Invention
The present invention relates generally to methods for fabricating magnetic sensor elements. More particularly, the present invention relates to methods for fabricating non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements.
2. Description of the Related Art
The recent and continuing advances in computer and information technology have been made possible not only by the correlating advances in the functionality, reliability and speed of semiconductor integrated circuits, but also by the correlating advances in the storage density and reliability of direct access storage devices (DASDs) employed in digitally encoded magnetic data storage and retrieval.
Storage density of direct access storage devices (DASDs) is typically determined as areal storage density of a magnetic data storage medium formed upon a rotating magnetic data storage disk within a direct access storage device (DASD) magnetic data storage enclosure. The areal storage density of the magnetic data storage medium is defined largely by the track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium. The track width, the track spacing and the linear magnetic domain density within the magnetic data storage medium are in turn determined by several principal factors, including but not limited to: (1) the magnetic read-write characteristics of a magnetic read-write head employed in reading and writing digitally encoded magnetic data from and into the magnetic data storage medium; (2) the magnetic domain characteristics of the magnetic data storage medium; and (3) the separation distance of the magnetic read-write head from the magnetic data storage medium.
With regard to the magnetic read-write characteristics of magnetic read-write heads employed in reading and writing digitally encoded magnetic data from and into a magnetic data storage medium, it is known in the art of magnetic read-write head fabrication that magnetoresistive (MR) sensor elements employed within magnetoresistive (MR) read-write heads are generally superior to other types of magnetic sensor elements when employed in retrieving digitally encoded magnetic data from a magnetic data storage medium. In that regard, magnetoresistive (MR) sensor elements are generally regarded as superior since magnetoresistive (MR) sensor elements are known in the art to provide high output digital read signal amplitudes, with good linear resolution, independent of the relative velocity of a magnetic data storage medium with respect to a magnetoresistive (MR) read-write head having the magnetoresistive (MR) sensor element incorporated therein.
Within the general category of magnetoresistive (MR) sensor elements, magnetoresistive (MR) sensor elements which employ multiple magnetoresistive (MR) layers (typically including a pair of magnetoresistive (MR) layers), such as but not limited to dual stripe magnetoresistive (DSMR) sensor elements and spin valve magnetoresistive (SVMR) sensor elements, and in particular magnetoresistive (MR) sensor elements which employ multiple magnetoresistive (MR) layers at least one of which is magnetically biased to provide non-parallel magnetic bias directions of the multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements, such as nominally anti-parallel longitudinally magnetically biased dual stripe magnetoresistive (DSMR) sensor elements and nominally perpendicularly magnetically biased spin valve magnetoresistive (SVMR) sensor elements, are presently of considerable interest insofar as the magnetically biased magnetoresistive (MR) layers employed within such magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements typically provide enhanced magnetic read signal amplitude and fidelity in comparison with single stripe magnetoresistive (MR) sensor elements, non-magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements and parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements.
While non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements such as but not limited to nominally anti-parallel longitudinally magnetically biased dual stripe magnetoresistive (DSMR) sensor elements and nominally perpendicularly magnetically biased spin valve magnetoresistive (SVMR) sensor elements are thus desirable within the art of digitally encoded magnetic data storage and retrieval, non-parallel multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements are nonetheless not fabricated entirely without problems in the art of magnetoresistive (MR) sensor element fabrication. In particular, it is often difficult to form non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements with optimal and enhanced magnetic properties since a magnetic biasing of a later formed magnetoresistive (MR) layer within a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element will often compromise a magnetic biasing of an earlier formed magnetoresistive (MR) layer within the non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element.
It is thus towards the goal of providing, for use within magnetic data storage and retrieval, a method for forming a non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element with optimal and enhanced magnetic properties, that the present invention is most generally directed.
Various methods and resultant magnetoresistive (MR) sensor element structures have been disclosed in the art of magnetoresistive (MR) sensor element fabrication for forming magnetically biased magnetoresistive (MR) sensor elements with enhanced functionality, enhanced reliability or other desirable properties.
For example, Mao et al., in U.S. Pat. No. 5,764,056, discloses a spin valve magnetoresistive (SVMR) sensor element which simultaneously possesses an enhanced thermal stability and an enhanced pinning field. To realize the foregoing objects, the spin valve magnetoresistive (SVMR) sensor element employs a pinned ferromagnetic material layer of thickness less than about 100 angstroms, wherein the pinned ferromagnetic material layer has formed laminated thereupon a nickel-manganese alloy antiferromagnetic pinning material layer of thickness less than about 200 angstroms.
In addition, Uno et al., in U.S. Pat. No. 5,772,794, discloses a method for forming a spin valve magnetoresistive (SVMR) sensor element, wherein there is provided an enhanced magnetic anisotropy within a pinned magnetoresistive (MR) layer within the spin valve magnetoresistive (SVMR) sensor element. The method realizes the foregoing object by employing when fabricating the spin valve magnetoresistive (SVMR) sensor element a final heat treatment step, where the final heat treatment step employs application of a magnetic field in a direction perpendicular to a track width direction of the spin valve magnetoresistive (SVMR) sensor element so that the pinned magnetoresistive (MR) layer within the spin valve magnetoresistive (SVMR) sensor element is pinned by a pinning material layer within the spin valve magnetoresistive (SVMR) sensor element with the enhanced uniaxial anisotropy.
Further Hoshiya et al., in U.S. Pat. No. 5,843,589, disclose a magnetoresistive (MR) sensor element, and a magnetic data storage system which employs the magnetoresistive (MR) sensor element, where the magnetoresistive (MR) sensor element has an enhanced exchange coupling and an enhanced thermal stability. To realize the foregoing objects, the magnetoresistive (MR) sensor element employs a cobalt or cobalt alloy ferromagnetic material layer having laminated thereupon an antiferromagnetic material layer formed of a chromium-manganese based alloy.
Finally, Gill, in U.S. Pat. No. 5,867,351, discloses a spin valve magnetoresistive (SVMR) sensor element where an antiferromagnetic pinning material layer within the spin valve magnetoresistive (SVMR) sensor element pins a ferromagnetic pinned layer with the spin valve magnetoresistive (SVMR) sensor element with a high coercivity while simultaneously not significantly impacting the coercivity of a ferromagnetic free layer within the spin valve magnetoresistive (SVMR) sensor element. The spin valve magnetoresistive (SVMR) sensor element realizes the foregoing object by employing when forming the spin valve magnetoresistive (SVMR) sensor element the antiferromagnetic pinning material layer formed of an amorphous magnetic material, such as a terbium-iron-cobalt amorphous magnetic material or a samarium-cobalt amorphous magnetic material, which possesses a high magnetic coercivity and a low magnetic moment.
Desirable within the art of non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor element fabrication are additional methods and materials which may be employed for forming non-parallel magnetically biased multiple magnetoresistive (MR) layer magnetoresistive (MR) sensor elements with optimal and enhanced magnetic properties.
It is towards the foregoing object that the present invention is directed.